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/* (C) 1999-2001 Paul `Rusty' Russell
* (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/types.h>
#include <linux/export.h>
#include <linux/init.h>
#include <linux/udp.h>
#include <linux/tcp.h>
#include <linux/icmp.h>
#include <linux/icmpv6.h>
#include <linux/dccp.h>
#include <linux/sctp.h>
#include <net/sctp/checksum.h>
#include <linux/netfilter.h>
#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_nat_core.h>
#include <net/netfilter/nf_nat_l3proto.h>
#include <net/netfilter/nf_nat_l4proto.h>
static void
__udp_manip_pkt(struct sk_buff *skb,
const struct nf_nat_l3proto *l3proto,
unsigned int iphdroff, struct udphdr *hdr,
const struct nf_conntrack_tuple *tuple,
enum nf_nat_manip_type maniptype, bool do_csum)
{
__be16 *portptr, newport;
if (maniptype == NF_NAT_MANIP_SRC) {
/* Get rid of src port */
newport = tuple->src.u.udp.port;
portptr = &hdr->source;
} else {
/* Get rid of dst port */
newport = tuple->dst.u.udp.port;
portptr = &hdr->dest;
}
if (do_csum) {
l3proto->csum_update(skb, iphdroff, &hdr->check,
tuple, maniptype);
inet_proto_csum_replace2(&hdr->check, skb, *portptr, newport,
false);
if (!hdr->check)
hdr->check = CSUM_MANGLED_0;
}
*portptr = newport;
}
static bool udp_manip_pkt(struct sk_buff *skb,
const struct nf_nat_l3proto *l3proto,
unsigned int iphdroff, unsigned int hdroff,
const struct nf_conntrack_tuple *tuple,
enum nf_nat_manip_type maniptype)
{
struct udphdr *hdr;
bool do_csum;
if (!skb_make_writable(skb, hdroff + sizeof(*hdr)))
return false;
hdr = (struct udphdr *)(skb->data + hdroff);
do_csum = hdr->check || skb->ip_summed == CHECKSUM_PARTIAL;
__udp_manip_pkt(skb, l3proto, iphdroff, hdr, tuple, maniptype, do_csum);
return true;
}
static bool udplite_manip_pkt(struct sk_buff *skb,
const struct nf_nat_l3proto *l3proto,
unsigned int iphdroff, unsigned int hdroff,
const struct nf_conntrack_tuple *tuple,
enum nf_nat_manip_type maniptype)
{
#ifdef CONFIG_NF_CT_PROTO_UDPLITE
struct udphdr *hdr;
if (!skb_make_writable(skb, hdroff + sizeof(*hdr)))
return false;
hdr = (struct udphdr *)(skb->data + hdroff);
__udp_manip_pkt(skb, l3proto, iphdroff, hdr, tuple, maniptype, true);
#endif
return true;
}
static bool
sctp_manip_pkt(struct sk_buff *skb,
const struct nf_nat_l3proto *l3proto,
unsigned int iphdroff, unsigned int hdroff,
const struct nf_conntrack_tuple *tuple,
enum nf_nat_manip_type maniptype)
{
#ifdef CONFIG_NF_CT_PROTO_SCTP
struct sctphdr *hdr;
int hdrsize = 8;
/* This could be an inner header returned in imcp packet; in such
* cases we cannot update the checksum field since it is outside
* of the 8 bytes of transport layer headers we are guaranteed.
*/
if (skb->len >= hdroff + sizeof(*hdr))
hdrsize = sizeof(*hdr);
if (!skb_make_writable(skb, hdroff + hdrsize))
return false;
hdr = (struct sctphdr *)(skb->data + hdroff);
if (maniptype == NF_NAT_MANIP_SRC) {
/* Get rid of src port */
hdr->source = tuple->src.u.sctp.port;
} else {
/* Get rid of dst port */
hdr->dest = tuple->dst.u.sctp.port;
}
if (hdrsize < sizeof(*hdr))
return true;
if (skb->ip_summed != CHECKSUM_PARTIAL) {
hdr->checksum = sctp_compute_cksum(skb, hdroff);
skb->ip_summed = CHECKSUM_NONE;
}
#endif
return true;
}
static bool
tcp_manip_pkt(struct sk_buff *skb,
const struct nf_nat_l3proto *l3proto,
unsigned int iphdroff, unsigned int hdroff,
const struct nf_conntrack_tuple *tuple,
enum nf_nat_manip_type maniptype)
{
struct tcphdr *hdr;
__be16 *portptr, newport, oldport;
int hdrsize = 8; /* TCP connection tracking guarantees this much */
/* this could be a inner header returned in icmp packet; in such
cases we cannot update the checksum field since it is outside of
the 8 bytes of transport layer headers we are guaranteed */
if (skb->len >= hdroff + sizeof(struct tcphdr))
hdrsize = sizeof(struct tcphdr);
if (!skb_make_writable(skb, hdroff + hdrsize))
return false;
hdr = (struct tcphdr *)(skb->data + hdroff);
if (maniptype == NF_NAT_MANIP_SRC) {
/* Get rid of src port */
newport = tuple->src.u.tcp.port;
portptr = &hdr->source;
} else {
/* Get rid of dst port */
newport = tuple->dst.u.tcp.port;
portptr = &hdr->dest;
}
oldport = *portptr;
*portptr = newport;
if (hdrsize < sizeof(*hdr))
return true;
l3proto->csum_update(skb, iphdroff, &hdr->check, tuple, maniptype);
inet_proto_csum_replace2(&hdr->check, skb, oldport, newport, false);
return true;
}
static bool
dccp_manip_pkt(struct sk_buff *skb,
const struct nf_nat_l3proto *l3proto,
unsigned int iphdroff, unsigned int hdroff,
const struct nf_conntrack_tuple *tuple,
enum nf_nat_manip_type maniptype)
{
#ifdef CONFIG_NF_CT_PROTO_DCCP
struct dccp_hdr *hdr;
__be16 *portptr, oldport, newport;
int hdrsize = 8; /* DCCP connection tracking guarantees this much */
if (skb->len >= hdroff + sizeof(struct dccp_hdr))
hdrsize = sizeof(struct dccp_hdr);
if (!skb_make_writable(skb, hdroff + hdrsize))
return false;
hdr = (struct dccp_hdr *)(skb->data + hdroff);
if (maniptype == NF_NAT_MANIP_SRC) {
newport = tuple->src.u.dccp.port;
portptr = &hdr->dccph_sport;
} else {
newport = tuple->dst.u.dccp.port;
portptr = &hdr->dccph_dport;
}
oldport = *portptr;
*portptr = newport;
if (hdrsize < sizeof(*hdr))
return true;
l3proto->csum_update(skb, iphdroff, &hdr->dccph_checksum,
tuple, maniptype);
inet_proto_csum_replace2(&hdr->dccph_checksum, skb, oldport, newport,
false);
#endif
return true;
}
static bool
icmp_manip_pkt(struct sk_buff *skb,
const struct nf_nat_l3proto *l3proto,
unsigned int iphdroff, unsigned int hdroff,
const struct nf_conntrack_tuple *tuple,
enum nf_nat_manip_type maniptype)
{
struct icmphdr *hdr;
if (!skb_make_writable(skb, hdroff + sizeof(*hdr)))
return false;
hdr = (struct icmphdr *)(skb->data + hdroff);
inet_proto_csum_replace2(&hdr->checksum, skb,
hdr->un.echo.id, tuple->src.u.icmp.id, false);
hdr->un.echo.id = tuple->src.u.icmp.id;
return true;
}
static bool
icmpv6_manip_pkt(struct sk_buff *skb,
const struct nf_nat_l3proto *l3proto,
unsigned int iphdroff, unsigned int hdroff,
const struct nf_conntrack_tuple *tuple,
enum nf_nat_manip_type maniptype)
{
struct icmp6hdr *hdr;
if (!skb_make_writable(skb, hdroff + sizeof(*hdr)))
return false;
hdr = (struct icmp6hdr *)(skb->data + hdroff);
l3proto->csum_update(skb, iphdroff, &hdr->icmp6_cksum,
tuple, maniptype);
if (hdr->icmp6_type == ICMPV6_ECHO_REQUEST ||
hdr->icmp6_type == ICMPV6_ECHO_REPLY) {
inet_proto_csum_replace2(&hdr->icmp6_cksum, skb,
hdr->icmp6_identifier,
tuple->src.u.icmp.id, false);
hdr->icmp6_identifier = tuple->src.u.icmp.id;
}
return true;
}
/* manipulate a GRE packet according to maniptype */
static bool
gre_manip_pkt(struct sk_buff *skb,
const struct nf_nat_l3proto *l3proto,
unsigned int iphdroff, unsigned int hdroff,
const struct nf_conntrack_tuple *tuple,
enum nf_nat_manip_type maniptype)
{
#if IS_ENABLED(CONFIG_NF_CT_PROTO_GRE)
const struct gre_base_hdr *greh;
struct pptp_gre_header *pgreh;
/* pgreh includes two optional 32bit fields which are not required
* to be there. That's where the magic '8' comes from */
if (!skb_make_writable(skb, hdroff + sizeof(*pgreh) - 8))
return false;
greh = (void *)skb->data + hdroff;
pgreh = (struct pptp_gre_header *)greh;
/* we only have destination manip of a packet, since 'source key'
* is not present in the packet itself */
if (maniptype != NF_NAT_MANIP_DST)
return true;
switch (greh->flags & GRE_VERSION) {
case GRE_VERSION_0:
/* We do not currently NAT any GREv0 packets.
* Try to behave like "nf_nat_proto_unknown" */
break;
case GRE_VERSION_1:
pr_debug("call_id -> 0x%04x\n", ntohs(tuple->dst.u.gre.key));
pgreh->call_id = tuple->dst.u.gre.key;
break;
default:
pr_debug("can't nat unknown GRE version\n");
return false;
}
#endif
return true;
}
bool nf_nat_l4proto_manip_pkt(struct sk_buff *skb,
const struct nf_nat_l3proto *l3proto,
unsigned int iphdroff, unsigned int hdroff,
const struct nf_conntrack_tuple *tuple,
enum nf_nat_manip_type maniptype)
{
switch (tuple->dst.protonum) {
case IPPROTO_TCP:
return tcp_manip_pkt(skb, l3proto, iphdroff, hdroff,
tuple, maniptype);
case IPPROTO_UDP:
return udp_manip_pkt(skb, l3proto, iphdroff, hdroff,
tuple, maniptype);
case IPPROTO_UDPLITE:
return udplite_manip_pkt(skb, l3proto, iphdroff, hdroff,
tuple, maniptype);
case IPPROTO_SCTP:
return sctp_manip_pkt(skb, l3proto, iphdroff, hdroff,
tuple, maniptype);
case IPPROTO_ICMP:
return icmp_manip_pkt(skb, l3proto, iphdroff, hdroff,
tuple, maniptype);
case IPPROTO_ICMPV6:
return icmpv6_manip_pkt(skb, l3proto, iphdroff, hdroff,
tuple, maniptype);
case IPPROTO_DCCP:
return dccp_manip_pkt(skb, l3proto, iphdroff, hdroff,
tuple, maniptype);
case IPPROTO_GRE:
return gre_manip_pkt(skb, l3proto, iphdroff, hdroff,
tuple, maniptype);
}
/* If we don't know protocol -- no error, pass it unmodified. */
return true;
}
EXPORT_SYMBOL_GPL(nf_nat_l4proto_manip_pkt);
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